Modern agriculture, particularly in more arid regions, is increasingly turning to the use of circular cultivation and irrigation techniques for increased yields and farming efficiency. Circular cultivation involves the use an a long boom which rotates radially around a central pivot. The boom is supported above the ground by pylons. The bottom ends of the pylons are connected to wheels while the upper ends support the boom. The boom functions by irrigating the crops with water received via the central pivot as it rotates radially on the connected wheels. This is a very efficient way of irrigating large areas of land. As the boom swings around the central pivot in a controlled fashion, predetermined amounts of water are dispensed. The process lends itself readily to automation. Large areas of agricultural land can be efficiently farmed using this process. The efficiency of the process has made it very popular, as evidenced by the distinctive circular patterns of cultivated farmland frequently observed by air travelers in the American Mid-west.
While circular cultivation has proven very efficient in some aspects (e.g., irrigation), the resulting distinctive circular patterns of crops, commonly referred to as "crop-circles", are more difficult to manage in other aspects. This is especially true in the case of crop-dusting.
Crop-dusting is the term generally used for the dispensing of chemicals (e.g., fertilizers, pesticides, and the like) to an agricultural field (e.g., field crops, orchards, etc.) from an aircraft. During crop-dusting, the dispensing aircraft makes numerous sequential, adjacent passes, dispensing chemicals in a swath across the field in each pass. The aircraft's pilot carefully follows a flight path which ensures that each successive swath over the field is correctly spaced, distance wise, from the previous swath in order to avoid gaps or overlaps in coverage. For example, should one swath occur too far from a previous swath, the area of the field will not receive an sufficient amount of chemicals (e.g., pesticides, fertilizer, herbicides, and the like). Similarly, should one swath occur too close to a previous swath, the overlap area receives excessive amounts of chemicals. This can prove very expensive to the farmer. The crops of the field can be damaged or rendered unusable.
The circular pattern of the crops circles makes aircraft crop-dusting operations more difficult. Conventional, rectangular, agriculture fields, having neatly ordered rows of crops laid out in a rectangular pattern, readily lend themselves to the orderly, rank and file, back and forth maneuvers of a crop-dusting aircraft. Typically, the pilot guides the crop dusting aircraft up and down the rectangular field parallel to its rows, keeping track of progress by counting the rows covered. The physical layout of conventional, rectangular agriculture fields aid the pilot in making sure that the agricultural field is covered evenly. With crop circles however, it is more difficult for the pilot to keep track of his location and of what portion of the field is done. To enhance the efficiency of the crop dusting process, several navigation aids (navaids) using sophisticated guidance and positioning techniques, including GPS have been developed.
For example, US Patent number 4,225,226 issued to Davidson, et al., discloses a laser guidance system for crop dusting aircraft. U.S. Pat. No. 5,334,987 issued to Teach discloses a GPS based system for continuously tracking aircraft location and for automatically dispensing chemicals based upon the aircraft's GPS determined position with respect to the agricultural field. There is a problem, however, in that while these solutions are effective with rectangular agriculture fields, they are less efficient with crop circles. Each of the above prior art solutions were developed for use with the more prevalent conventional, rectangular fields. These conventional GPS crop dusting aids are designed to function with rectangular, rank and file, row by row, form of agricultural fields. In the case of crop circles, there are no neatly laid out, parallel rows. There are no equal length files of crops. The rows, if any, are circular and concentric, following the pattern traced out by the boom as it rotates around the central pivot. As such, the usual guidance cues of the rectangular agriculture fields are missing.
Several techniques have been attempted to adapt the above prior art solutions to use with crop circles. These techniques include, for example, cross flying. Cross flying involves the use of a navigation reference baseline external to the crop-circle. The use of the reference baseline allows the prior art navaids to model the crop circle as if it where a conventional rectangular field. The crop circle is then cross-flown, where the aircraft flies parallel swaths in one direction, rastering across the field, and subsequently flies parallel swaths in an orthogonal direction, to ensure coverage. Hence, much of the crop circle is over-flown twice or more. This has a number of undesirable consequences (e.g., increases flight time, materials, and costs).
For example, multiple over-flights potentially leads to over-dispensing of chemicals. The chemicals can be very expensive. In addition, as described above, over coverage can have detrimental effects on the crops. Another undesirable consequence is the fact that the aircraft unavoidably flies through the lingering aerosol clouds of its own spray. Depending upon the chemicals being dispensed, this can be extremely undesirable. The chemicals may be very harmful to the aircraft and to the pilot. Also, repeated over-flights disturbs the spray aerosol of the swaths, not allowing the aerosol clouds of the swaths to settle slowly and evenly onto the crops below.
Thus, what is needed is a method and system which specifically accounts for the form factor of a crop circle. What is needed is a system which gives the pilot a precise point of entry onto the crop circle, and which positions the point of entry such that the pilot has an unmistakable visual reference. What is needed is a system which provides accurate guidance commands such that the entire crop circle can be covered without any gaps or overlaps, and without requiring the crop dusting aircraft to fly through its own spray. What is needed is a system which makes efficient use of flight time, covering the crop circle in a minimum amount of time. The present invention provides a novel solution to the above needs.